Hello!
I'll visit Slovenia next summer! We'll go to Southern Austria in the holiday ( Villach) and I'm sure we'll spend some days in beautiful Slovenia as well. We'll probably visit Bled, Ljubljana, Triglav and maybe Koper, and maybe some other towns too. So I hope you can give me some advice on how I can get some bills (and maybe hits? ) from Slovenia! Can I exchange at banks? Which notes can I get from an ATM?
I hope you can help me!

You can get , and at the ATM. Till now i didn't have any problems with changing money at banks. When i asked they changed me, costumer or no costumer. They even went to get bundles from the safe and i had to wait 10-15 minutes.

No problem at any bank so far to exchange notes. In smaller places post office is an option, though they don't have so many notes on hand. When quantity isn't so important but you just want to collect another city or dot, I didn't have any problem at supermarkets (Mercator is most commonly found in villages, sometimes Tuš) or petrol stations, they are happy to help you with change if they have it.

If you go to the coast, Piran and Strunjan (Mesečev zaliv = Moon bay) are best, though Koper old town is also nice. BTW, Triglav is the highest mountain in Slovenia, don't confuse Slovenians if you actually mean Triglav National Park